This invention relates generally to improvements in and to adhesive attachments of the type designed for bonded affixation to a selected substrate, such as an adhesive stud attachment of the general type disclosed in U.S. Pat. Nos. 4,778,702 and 4,842,912. More specifically, this invention relates to an improved attachment assembly for use in a high temperature environment, particularly such as supporting and retaining an insulation blanket or the like on a substrate such as an aircraft engine nacelle to shield surrounding structures and components from heat generated during engine operation. The improved attachment assembly includes an insulated cap fastener for safeguarding a stud attachment against debonding in response to high temperature exposure.
Adhesive bonded attachments are generally known in the art for connecting a selected component such as a threaded stud or bolt onto a selected substrate such as a panel or other frame component in an aerospace or automotive application or the like. Such adhesive attachments typically include a base defining a bonding surface adapted to receive a selected curable bonding agent, whereupon the base is then pressed against the selected substrate for the duration of bonding agent cure time. In preferred attachment designs, a temporary attachment member or fixture is provided for temporary connection to or engagement with the substrate in a manner functioning to urge or draw the base bonding surface firmly against the substrate until the bonding agent is substantially completely cured. As a result, the adhesive bonded attachment is affixed to the substrate with a substantially optimized adhesive attachment force. Exemplary adhesive bonded stud attachments having a fastener element such as a threaded stud or bolt projecting from a radially enlarged base defining the bonding surface are disclosed in U.S. Pat. Nos. 4,778,702; 4,842,912; 4,822,565; and 4,668,546, which are incorporated by reference herein.
Such adhesive bonded stud attachments have been used for supporting and retaining an insulation blanket on a substrate enclosing a relatively high temperature compartment, wherein the insulation blanket is designed to heat-shield surrounding structures and components. Specifically, such insulation blankets have been mounted at the inboard side of an aircraft engine nacelle. In a typical installation, the insulation blanket comprises a suitable refractory cloth material carrying multiple grommets defining a corresponding plurality of mounting ports formed in the blanket. A plurality of adhesive bonded stud attachments are affixed onto an inboard side of the nacelle substrate at positions for stud reception into and through the grommet-defined mounting ports in the insulation blanket. Fastener nuts or the like are then secured to the ends of the studs for retaining the insulation blanket thereon at the inboard side of the nacelle substrate.
Use of adhesive bonded stud attachments for mounting an insulation blanket onto an aircraft engine nacelle or the like has, in the past, provided effective heat-shielding of adjacent structures and components to safeguard against heat damage during normal engine operation. In this regard, adhesive bonding agents have been available to withstand temperatures associated with thermal transmission along the fastener nuts and studs, and/or metal grommets on the insulation blanket, without significant risk or thermal-induced debonding of the stud attachment from the substrate. However, more recent aircraft engines have been designed to operate at significantly higher temperatures exceeding the thermal capacity of such bonding agents, whereby the adhesive-mounted stud attachment can debond or separate from the nacelle substrate. Such failure of the stud attachment can undesirably expose the substrate and adjoining components to thermal damage.
There exists, therefore, a significant need for further improvements in and to adhesive bonded attachment assemblies particularly of the type used in a high temperature environment such as mounting an insulation blanket onto a supporting aircraft engine nacelle substrate or the like, wherein such improved attachment assembly is designed to withstand significantly higher engine operating temperatures without risk of thermal debonding from the substrate. The present invention fulfills these needs and provides further related advantages.